This invention pertains to a replaceable pressure-tight inspection plug assembly adapted for use in inspecting the interior of a pressure vessel, and to a method for conveniently removing and replacing the plug pressure-tightly in the vessel wall using a mating rotatable machining tool.
During the normal course of operation of pressure vessels, such as those operating at 500-5000 psig. pressure, it is often desirable or necessary to inspect internal components of the vessel, such as during the warranty period or following extended periods of operation. Various inspection means or openings have been provided for making such internal inspections of pressurized equipment, such as bolted flanges, weld caps, and the like. However, such inspection openings using bolted flanges is usually not suitable because of potential gasket leakage problems. Also, inspection openings involving welded joints are usually difficult and time-consuming to remove and replace, and may require a stress relieving step following rewelding. For these reasons, there has been a need for a simpler inspection plug which can be removed with a minimum of time and labor expense. The present inspection plug assembly not only permits good visibility of the vessel internal areas and thus prevents or limits any internal failure by providing inspection capability, but also is pressure-tight and convenient to remove and replace.